id mind his own business. its his bo problem that he stocked his aquarium with the wrong fish. in the end his tiger barbs will end up the winner in that tank. fin nipping the angels & goldies_________________Martin
70 gallon tank with 11 various kind of fish
Pond with 3 goldfish

I would have a chat to the owner - he might not know anything about fish and just picked fish that he likes without asking questions. You never know, he might ask you to sort the tank out, and you'd get free meals for life...

I would certainly say something. As long as you do it in a non-confrontational manner, I don't see how anyone would have a problem.

Honestly, one would figure that a restaraunt owner would want to have a succesful and good looking tank in his establishment since ambiance is a huge part of a restaraunts success. Hey, who knows, maybe you can turn it into a maintainance job for some 'fun money'? (Since the owner obviously got some bad advice or bought from an uncaring, unhelpful shop).